package class06;

import sun.nio.cs.FastCharsetProvider;

import java.util.Stack;

/**
 * @author zhangchaoliang
 * create 2022
 */
public class IsPalindromeList {

    public static class Node{
        public int value;
        public Node next;

        public Node(int data){
            this.value=data;
        }
    }

    public static boolean isPalindrome1(Node head){
        Stack<Node> stack = new Stack<>();
        Node cur = head;
        while (cur!=null){
            stack.push(cur);
            cur =cur.next;
        }
        while (head!=null){
            if (head.value!=stack.pop().value){
                return false;
            }
            head = head.next;
        }
        return true;
    }

    public static boolean isPalindrome2(Node head){
        if (head==null||head.next==null){
            return true;
        }
        Node right = head.next;
        Node cur = head;
        while (cur.next!=null&&cur.next.next!=null){
            right = right.next;
            cur=cur.next.next;
        }
        Stack<Node> stack = new Stack<>();
        while (right!=null){
            stack.push(right);
            right=right.next;
        }
        while (!stack.isEmpty()){
            if (head.value!=stack.pop().value){
                return false;
            }
            head = head.next;
        }
        return true;
    }

    public static boolean isPalindrome3(Node head){
        if (head==null||head.next==null){
            return true;
        }
        Node n1=head;
        Node n2=head;
        while (n2.next!=null&&n2.next.next!=null){
            n1 = n1.next;
            n2=n2.next.next;
        }

        n2 = n1.next;
        n1.next = null;
        Node n3 = null;
        while (n2!=null){
            n3 = n2.next;
            n2.next = n1;
            n1=n2;
            n2=n3;
        }
        n3 = n1;
        n2 = head;
        boolean res = true;
        while (n1!=null&&n2!=null){
            if (n1.value!=n2.value){
                res = false;
                break;
            }
            n1=n1.next;
            n2=n2.next;
        }
        n1=n3.next;
        n3.next=null;
        while (n1!=null){
            n2 = n1.next;
            n1.next = n3;
            n3 = n1;
            n1=n2;
        }
        return res;
    }

    public static void printLinkedList(Node node){
        System.out.println("Linked List: ");
        while (node!=null){
            System.out.println(node.value+" ");
            node = node.next;
        }
        System.out.println();
    }

    public static void main(String[] args) {

        Node head = null;
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

        head = new Node(1);
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

        head = new Node(1);
        head.next = new Node(2);
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

        head = new Node(1);
        head.next = new Node(1);
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

        head = new Node(1);
        head.next = new Node(2);
        head.next.next = new Node(3);
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

        head = new Node(1);
        head.next = new Node(2);
        head.next.next = new Node(1);
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

        head = new Node(1);
        head.next = new Node(2);
        head.next.next = new Node(3);
        head.next.next.next = new Node(1);
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

        head = new Node(1);
        head.next = new Node(2);
        head.next.next = new Node(2);
        head.next.next.next = new Node(1);
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

        head = new Node(1);
        head.next = new Node(2);
        head.next.next = new Node(3);
        head.next.next.next = new Node(2);
        head.next.next.next.next = new Node(1);
        printLinkedList(head);
        System.out.print(isPalindrome1(head) + " | ");
        System.out.print(isPalindrome2(head) + " | ");
        System.out.println(isPalindrome3(head) + " | ");
        printLinkedList(head);
        System.out.println("=========================");

    }

}
